/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineMessageInterface.h
virtual [FDelegateHandle](API\Runtime\Core\Delegates\FDelegateHandle) AddOnSendMessageCompleteDelegate_Handle ( int32 LocalUserNum, const [FOnSendMessageCompleteDelegate](API\Plugins\OnlineSubsystem\Interfaces\FOnSendMessageCompleteDelegate) & Delegate )